can't cross build llvm

[z-erica]

lots of errors near the end of the build such as:

[228/1045] Building GenVT.inc...
FAILED: [code=126] include/llvm/CodeGen/GenVT.inc /builddir/llvm-21.1.4/build/NATIVE/include/llvm/CodeGen/GenVT.inc 
cd /builddir/llvm-21.1.4/build/NATIVE/include/llvm/CodeGen && /builddir/llvm-21.1.4/build/NATIVE/bin/llvm-min-tblgen -gen-vt -I/builddir/llvm-21.1.4/llvm/include/llvm/CodeGen -I/builddir/llvm-21.1.4/build/NATIVE/include -I/builddir/llvm-21.1.4/llvm/include /builddir/llvm-21.1.4/llvm/include/llvm/CodeGen/ValueTypes.td --write-if-changed -o GenVT.inc -d GenVT.inc.d && /usr/bin/cmake -E cmake_transform_depfile Ninja gccdepfile /builddir/llvm-21.1.4/llvm /builddir/llvm-21.1.4/llvm/include/llvm/CodeGen /builddir/llvm-21.1.4/build/NATIVE /builddir/llvm-21.1.4/build/NATIVE/include/llvm/CodeGen /builddir/llvm-21.1.4/build/NATIVE/include/llvm/CodeGen/GenVT.inc.d /builddir/llvm-21.1.4/build/NATIVE/CMakeFiles/d/fcbe3f4ebaf9e5dc2ec66d35eede83df3ab8d2f46d48a4a254911470550e19cf.d
/bin/sh: /builddir/llvm-21.1.4/build/NATIVE/bin/llvm-min-tblgen: Exec format error
[229/1045] Building AArch64TargetParserDef.inc...
FAILED: [code=126] include/llvm/TargetParser/AArch64TargetParserDef.inc /builddir/llvm-21.1.4/build/NATIVE/include/llvm/TargetParser/AArch64TargetParserDef.inc 
cd /builddir/llvm-21.1.4/build/NATIVE/include/llvm/TargetParser && /builddir/llvm-21.1.4/build/NATIVE/bin/llvm-min-tblgen -gen-arm-target-def -I/builddir/llvm-21.1.4/llvm/include/llvm/TargetParser -I/builddir/llvm-21.1.4/llvm/lib/Target/AArch64 -I/builddir/llvm-21.1.4/build/NATIVE/include -I/builddir/llvm-21.1.4/llvm/include /builddir/llvm-21.1.4/llvm/lib/Target/AArch64/AArch64.td --write-if-changed -o AArch64TargetParserDef.inc -d AArch64TargetParserDef.inc.d && /usr/bin/cmake -E cmake_transform_depfile Ninja gccdepfile /builddir/llvm-21.1.4/llvm /builddir/llvm-21.1.4/llvm/include/llvm/TargetParser /builddir/llvm-21.1.4/build/NATIVE /builddir/llvm-21.1.4/build/NATIVE/include/llvm/TargetParser /builddir/llvm-21.1.4/build/NATIVE/include/llvm/TargetParser/AArch64TargetParserDef.inc.d /builddir/llvm-21.1.4/build/NATIVE/CMakeFiles/d/913b45d3f654e5f9b831944f02920fe9436835403c72d29c1300aeeb0bc54ee7.d
/bin/sh: /builddir/llvm-21.1.4/build/NATIVE/bin/llvm-min-tblgen: Exec format error